diff --git a/src/interpreter/bytecode-interpreter.dasc b/src/interpreter/bytecode-interpreter.dasc
diff --git a/src/interpreter/bytecode-interpreter.dasc.pp.cc b/src/interpreter/bytecode-interpreter.dasc.pp.cc
diff --git a/src/parser/optimizer.cc b/src/parser/optimizer.cc
@@ -677,17 +677,17 @@ bool ExpressionOptimizer::Optimize( ast::Binary* node , Expression* expr ) {
         case Token::TK_SUB:
           if(lhs.IsInteger() && lhs.int_value == 0) {
             lava_verify( rhs.IsComplex() );
-            expr->node = rhs.node;
-          } else if(rhs.IsInteger() && rhs.int_value == 0) {
-            lava_verify( lhs.IsComplex() );
             if(node->op == Token::kAdd) {
-              expr->node = lhs.node;
+              expr->node = rhs.node;
             } else {
               expr->node = ast_factory_.NewUnary(node->start,
                                                  node->end,
                                                  Token::kSub,
                                                  lhs.node);
             }
+          } else if(rhs.IsInteger() && rhs.int_value == 0) {
+            lava_verify( lhs.IsComplex() );
+            expr->node = lhs.node;
           }
           break;
         case Token::TK_MUL:

diff --git a/unittest/interpreter/bytecode-interpreter-test.cc b/unittest/interpreter/bytecode-interpreter-test.cc
@@ -9,6 +9,8 @@
 #include <gtest/gtest.h>
 #include <cassert>
 #include <iostream>
+#include <gtest/gtest.h>
+#include <cmath>
 
 #include "src/interpreter/bytecode-interpreter.h"
 
@@ -36,38 +38,129 @@ bool Compile( Context* context ,const char* source ,
   return true;
 }
 
-} // namespace
-
+static const bool kShowBytecode = false;
 
-int main() {
-  lavascript::InitTrace("-");
+// Helper function to test *primitive* values
+bool PrimitiveEqual( const char* source , const Value& primitive ) {
+  // Generate assembler everytime, this is kind of slow but nothing hurts
   std::shared_ptr<lavascript::interpreter::AssemblyInterpreter>
     interp( lavascript::interpreter::AssemblyInterpreter::Generate() );
   lava_verify(interp);
-  {
-    lavascript::DumpWriter writer(NULL);
-    interp->Dump(&writer);
-  }
   lavascript::interpreter::AssemblyInterpreter::Instance ins(interp);
 
   Context ctx;
   std::string error;
-  std::string script(stringify(
-        var a = 10;
-        var b = 200;
-        return a + 50;
-        ));
-
+  std::string script(source);
   ScriptBuilder sb("a",script);
-  assert(Compile(&ctx,script.c_str(),&sb,&error));
-  DumpWriter dw;
-  sb.Dump(&dw);
+  lava_verify(Compile(&ctx,script.c_str(),&sb,&error));
+
+  if(kShowBytecode) {
+    DumpWriter dw;
+    sb.Dump(&dw);
+  }
+
   Handle<Script> scp( Script::New(ctx.gc(),&ctx,sb) );
   Handle<Object> obj( Object::New(ctx.gc()) );
   Value ret;
+
+  std::cout<<"-----------------------------------\n";
   bool r = ins.Run(&ctx,scp,obj,&error,&ret);
-  assert(r);
-  assert(ret.IsInteger());
-  std::cout<<ret.GetInteger()<<std::endl;
-  return r;
+  std::cout<<"-----------------------------------\n";
+
+  if(r) {
+    if(ret.IsNull()) {
+      return primitive.IsNull();
+    } else if(ret.IsReal()) {
+      return primitive.IsReal() ? (primitive.GetReal() == ret.GetReal()) : false;
+    } else if(ret.IsInteger()) {
+      return primitive.IsInteger() ? (primitive.GetInteger() == ret.GetInteger()) : false;
+    } else if(ret.IsBoolean()) {
+      return primitive.IsBoolean() ? (primitive.GetBoolean() == ret.GetBoolean()) : false;
+    } else {
+      lava_unreachF("not primitive type at all %s|%s",ret.type_name(),primitive.type_name());
+      return false;
+    }
+  } else {
+    return false;
+  }
+}
+
+#define PRIMITIVE_EQUAL(VALUE,...) \
+  ASSERT_TRUE(PrimitiveEqual(#__VA_ARGS__,::lavascript::Value(VALUE)))
+
+} // namespace
+
+namespace lavascript {
+namespace interpreter {
+
+TEST(Interpreter,ArithXV) {
+  PRIMITIVE_EQUAL(10,var a = 50; return 60-a;);
+  PRIMITIVE_EQUAL(30,var a = 10; return 20+a;);
+  PRIMITIVE_EQUAL(200,var a= 10; return 20*a;);
+  PRIMITIVE_EQUAL(5, var a= 10; return 50/a; );
+
+  PRIMITIVE_EQUAL(20.0,var a= 10.0; return 10.0+a;);
+  PRIMITIVE_EQUAL(20.0,var a= 10.0; return 30.0-a;);
+  PRIMITIVE_EQUAL(30.0,var a= 10.0; return 3.0*a; );
+  PRIMITIVE_EQUAL(3.0 ,var a= 10.0; return 30.0/a;);
+
+  PRIMITIVE_EQUAL(10.0,var a=50.0; return 60-a; );
+  PRIMITIVE_EQUAL(30.0,var a=10.0; return 20+a; );
+  PRIMITIVE_EQUAL(200.0,var a=10.0;return 20*a; );
+  PRIMITIVE_EQUAL(5.0, var a= 10.0;return 50/a; );
+
+  PRIMITIVE_EQUAL(20.0,var a= 10; return 10.0+a;);
+  PRIMITIVE_EQUAL(20.0,var a= 10; return 30.0-a;);
+  PRIMITIVE_EQUAL(30.0,var a= 10; return 3.0*a; );
+  PRIMITIVE_EQUAL(3.0 ,var a= 10; return 30.0/a;);
+
+  // Modula
+  PRIMITIVE_EQUAL(3,var a = 5; return 3 % a;);
+}
+
+TEST(Interpreter,ArithVX) {
+  PRIMITIVE_EQUAL(0,var a= 10; return a - 10; );
+  PRIMITIVE_EQUAL(30,var a= 20; return a + 10;);
+  PRIMITIVE_EQUAL(20,var a= 10; return a * 2 ; );
+  PRIMITIVE_EQUAL(10,var a= 20; return a / 2 ; );
+
+  PRIMITIVE_EQUAL(10.0,var a=6.0;return a + 4.0;);
+  PRIMITIVE_EQUAL(20.0,var a=24.0; return a - 4.0; );
+  PRIMITIVE_EQUAL(20.0,var a=10.0; return a * 2.0; );
+  PRIMITIVE_EQUAL(10.0 ,var a=20.0; return a / 2.0; );
+
+  PRIMITIVE_EQUAL(-10.0,var a=50.0; return a-60; );
+  PRIMITIVE_EQUAL(30.0,var a=10.0; return a+20; );
+  PRIMITIVE_EQUAL(200.0,var a=10.0;return a*20; );
+  PRIMITIVE_EQUAL(5.0, var a= 250.0;return a/50; );
+
+  PRIMITIVE_EQUAL(20.0,var a= 10; return a+10.0;);
+  PRIMITIVE_EQUAL(-20.0,var a= 10; return a-30.0;);
+  PRIMITIVE_EQUAL(30.0,var a= 10; return a*3.0; );
+  PRIMITIVE_EQUAL(5.0 ,var a= 10; return a/2.0;);
+
+  PRIMITIVE_EQUAL(3,var a= 3; return a % 5;);
+
+  PRIMITIVE_EQUAL(10.0,var a=10.0; return a-0;);
+}
+
+TEST(Interpreter,ArithPow) {
+  PRIMITIVE_EQUAL(static_cast<double>(std::pow(2,4)),var a = 4; return 2 ^ a;);
+  PRIMITIVE_EQUAL(static_cast<double>(std::pow(2,4)),var a = 4.0; return 2 ^ a;);
+  PRIMITIVE_EQUAL(static_cast<double>(std::pow(2,4)),var a = 4; return 2.0 ^ a;);
+  PRIMITIVE_EQUAL(static_cast<double>(std::pow(2,4)),var a = 4.0; return 2.0 ^ a;);
+
+  PRIMITIVE_EQUAL(static_cast<double>(std::pow(2,4)),var a = 2; return a ^ 4;);
+  PRIMITIVE_EQUAL(static_cast<double>(std::pow(2,4)),var a = 2.0; return a ^ 4;);
+  PRIMITIVE_EQUAL(static_cast<double>(std::pow(2,4)),var a = 2; return a ^ 4.0;);
+  PRIMITIVE_EQUAL(static_cast<double>(std::pow(2,4)),var a = 2.0; return a ^ 4.0;);
+}
+
+} // namespace lavascript
+} // namespace interpreter
+
+int main( int argc, char* argv[] ) {
+  ::lavascript::InitTrace("-");
+  testing::InitGoogleTest(&argc,argv);
+  return RUN_ALL_TESTS();
 }
diff --git a/unittest/parser/parser-test.cc b/unittest/parser/parser-test.cc
@@ -240,6 +240,8 @@ TEST(Parser,Expression) {
       for( var a = 100 ; ; 1 ) {}
       for( var a = 100 ; 200 ; ) {}
      );
+
+  positive( return a - 0; );
 }
 
 } // namespace parser